Vehicles commonly employ variable ratio transmissions to transfer power between an internal combustion engine and the vehicle wheels. In an automatic transmission, a controller selects the transmission ratio in response to the vehicle speed and a driver demand, usually communicated by depressing an accelerator pedal. In a Modular Hybrid Transmission (MHT) architecture, the vehicle also has a traction motor connected at the input of the transmission. The traction motor is electrically connected to a battery. The motor can be used in either a motoring mode in which energy from the battery is used to supplement the engine power or in a generating mode in which the motor converts mechanical energy into electrical energy which is stored in the battery.